Re: Radial Velocity Profile in Globular Clusters

Thus spake Richard Saam <rdsaam@xxxxxxx>
DRLunsford wrote:
See this paper by Scarpa et. al.
http://arxiv.org/abs/0707.2459
Quoting abstract:
"**It is shown that all clusters studied so far do behave like
galaxies, that is, their velocity dispersion profile flattens out at
large radii where the acceleration of gravity goes below 1e-8 cm/s/s,
instead of following the expected Keplerian fall off. In galaxies this
behavior is ascribed to the existence of a dark matter halo. Globular
clusters, however, do not contain dark matter**"

How is it concluded that Globular clusters
"do not contain dark matter"
if they have the "dark matter" characteristic related to
"velocity dispersion profile flattens out at large radii"?

Dark matter is generally assumed diffuse in galactic haloes - the size
of the galaxy being enough to provide the required mass. Globular
clusters are orders of magnitude smaller than galaxies and would require
large concentrations of dark matter to generate the velocity dispersion
profile. I would think that this could be eliminated by looking at the
gravitational effect of the cluster on surrounding galactic stars.

Regards

--
Charles Francis
moderator sci.physics.foundations.
substitute charles for NotI to email

.

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